1. Field of the Invention
This invention relates to improvements in electrical switches, and more particularly to improvements in spring switches of the type mountable on a circuit board substrate or the like.
2. Description of the Prior Art
Recently much emphasis has been placed upon the development of inexpensive miniature switches, for use, for example, in applications such as on the keyboards of pocket or desk size miniature calculators, and other apparatuses of similar size and physical similarity. To date, however, the switches which have been employed are usually either undesirably expensive, or require considerable precision in installation. The greater the degree of precision required for installation naturally increases the ultimate expense of the overall assembled switch.
One switch which has been advanced is a disk which is located directly over a number of wires or contacts between which electrical connection is desired. Upon application of a downward pressure upon the disk, it snaps from a generally concave posture in the direction of the contacts to a generally convex posture, thereby coming into contact with all of the desired contact elements. Usually such type switches are gold plated on their underside portions which contact the conductors to present minimum resistance when the switch is closed. However, because of the expense of the gold materials, the gold is plated only upon a minimum area on the disk. Consequently, precise alignment is required in the assembly of the disk upon the wires or other elements between which the switch connection is made.
In the manufacture of such disk devices, the disks are placed in holes of a previously formed mask, then a thin film of plastic or other flexible material is laid over the disks to secure them permanently to the printed circuit board within the proper position in the holes of the mask. Many problems are encountered, especially in the handling of the partially manufactured switches, in keeping the disks in the proper alignment upon the printed circuit board until the plastic or other protective layer is emplaced.
Finally, a key or other button type element is placed over the disk to transmit pressure thereto to cause it to snap from the concave to convex postures as above described.
Other types of snap switches have been proposed, such as multiple bar contacts and snap switch strips. The details of such switches can be seen in Product Engineering, September, 1972, page 42 et seq.
Nevertheless, in the installation of such switches, as mentioned above, a number of precision parts must be assembled, or the particular parts employed are of relatively high cost, especially with respect to the gold plated elements thereof.
Another disadvantage of the spring type switches heretofore advanced is that because of the number of parts, and the very precision alignment ordinarily required in their assembly, usually machine or automated assembly is impractical or highly inefficient. This is especially true in switches in which, for example, four or more relatively complicated component parts are stacked or aligned before connection upon a printed circuit board or the like.